The oncogenic potentials of Epstein-Barr virus (EBV) in nonhuman primates and the continuous demonstration of EBV genome in epithelial cells in nasopharyngeal carcinoma (NPC) and Burkitt's lymphoma (BL) provide strong evidence that this virus is one of the major contributing factors in the complex etiology of these tumors. Moreover, the oncogenicity of Herpesvirus saimiri (HVS) and Herpesvirus ateles (HVA) in nonhuman primates and in certain rodents, relates oncogenic herpesvirus to lymphoproliferative neoplasia. The international activities consisting of coordination between NCI Viral Oncology Program and W.H.O. International Reference Programs in Comparative Virology were continued. Under this activity we provided consultation, exchange of scientific data, personnel, reference reagents and collected data on comparative oncology from different parts of the world to relate to etiological factors in tumors from man and domestic animals. BIBLIOGRAPHIC REFERENCES: Ablashi, D.V., Twardzik, D.R., Easton, J.M., Armstrong, G.R., Luetzeler, J., Jasmin, C. and Cherman, J.C.: Effects of 5-tungsto-2-antimoniate in oncogenic DNA and RNA virus-cell system. Europ. J. Cancer, 1977, in press. Kruger, G.R.F., Samii, H., Sesterhenn, K., Uhlman, C.H., Ablashi, D.V., Fischer, R. and Wustrow, F.: Non-Hodgkin lymphomas: cell population and functional behavior. In Chierfelder, S., Rodt, H. and Thid, E. (Eds.): Immunol. Diagnosis of Leukemia and Lymphomas. J.F. Lehmanns, Verlag, Munich, Germany, 1977, in press.